Morality from the ground up

[Astonished]

Non-arbitrary? How about the fact that there are many disorders that can occur from cannibalism of our own species?

Or just the fact that we're the only species capable of discussing this topic and making conscious choices. No other species can really render their opinion.

Obviously, the dietary consideration is not the point.  The point is about how we choose to extend the moral umbrella from self, to family and friends, from community to nation, and then to all humanity, and (for some of us) to animals as well (starting with cute l'il baby seals and ending at mosquitoes-- because FUCK mosquitoes!)

Is there a rational reason why the suffering of one living thing matters less than that of others?  Is not suffering itself bad, and the knowing causing of it wrong?

The experience of a contemplative being, us being the pinnacle (as far as we know) then it's fair to say our capacity for suffering and joy are far greater than that of less sapient organisms, so that is at least a consideration. So if a few lab animals have to die from faulty drugs that will eventually lead to the discovery of a medication that will enable a parent of several young children to live rather than die and leave them and their other parent without them and their support, that's easy to justify because the amount of suffering that would otherwise cause to that family is massive, whereas that animal is not likely to have a family capable of mourning it, at least not when it's reached adulthood. Not to mention that handful of animal deaths can lead to hundreds of saved human lives over future generations. So there's a numbers game component as well.